The 3-year-old's body was spotted near shore in Bayou La Fourche Bay, about three miles west of where the infant was found, authorities said.
Cochran said the remaining two bodies could be in the same area or shifted by current closer to the Alabama-Mississippi line. The search will resume Monday and is expected to concentrate on the marshes along the shore.
"Everyone should be on the lookout," Cochran said.
The search for the children -- ranging in age from a few months to 3 years -- began Tuesday near the mouth of Mobile Bay after prosecutors said the father, Lam Luong, confessed.
The children's mother, 23-year-old Kieu Phan, had gone with Luong to report them missing Monday evening.
After the infant's body was found Saturday, authorities expanded the search zone westward toward Pascagoula, Miss., believing that the strong currents may have moved the remaining bodies in that direction.
As helicopters and airplanes searched, airboats shuttled volunteers into the shallow mud-boggy shoreline, with some walking hand-in-hand in a slow stroll, upending logs and probing debris dumped by the high tide.
Luong, 37, a shrimp boat worker who lives in Irvington, was being held without bond on four counts of capital murder. If convicted, he could be sentenced to death or life in prison without parole.
District Attorney John Tyson Jr. said Luong had confessed to throwing Ryan Phan, 3, Hannah Luong, 2, Lindsey Luong, 1, and Danny Luong, 4 months, off the three-mile-long bridge after an argument with his wife.
Luong later recanted, claiming two Asian women took the children and never returned them. A witness saw him on the 80-foot-tall two-lane bridge with the children, and another saw him leave the area without the children, police said.
Luong's appointed attorney, Joe Kulakowski, attempted to meet with Luong on Sunday, but he said he was unable to arrange it with jail officials.
Kulakowski said he plans to ask the court on Monday to appoint a Vietnamese interpreter to help him overcome language barriers in speaking with Luong.
